1. Field of the Invention
The present invention relates to a lens apparatus which is used for, for example, a broadcasting television lens and includes movable optical members such as a zoom lens, a focus lens, and an aperture stop, which are drive-controlled by multiple demand devices.
2. Description of the Related Art
Systems for controlling movable optical members such as a zoom lens and a focus lens in a television camera are described in, for example, U.S. Pat. No. 7,145,737 and Japanese Patent Application Laid-Open No. H09-068640. In the systems, a lens body is connected with a zoom demand device for generating a demand signal for zoom drive and a focus demand device for generating a demand signal for focus drive.
In addition to the demand devices, multiple demand devices such as a demand device for generating an aperture stop demand signal and a demand device for controlling an anti-vibration optical system can be connected with the lens body. The lens body is cable-connected with each of the demand devices by using a multi-pin connector described in U.S. Pat. No. 7,145,737.
In a case of studio photographing, there is a tripod operation in which the television camera, a television lens, the zoom demand device, and the focus demand device are attached to a tripod. In addition to this, there is a shoulder-mounted operation in which the zoom demand device and the focus demand device are not used and the television camera and the television lens are combined with each other to be mounted on the shoulder of a camera operator.
FIG. 8 is a block diagram illustrating the conventional television photographing system described above. A zoom demand device 2 for operating a zoom lens of a lens body 1 can generate a return switch demand, a VTR switch demand, a shot demand, and a shot storage demand in addition to a zoom demand for zoom drive control. A focus demand device 3 for operating a focus lens of the lens body 1 can generate the same switch demands as those in the zoom demand device 2 in addition to a focus demand for focus drive control. The lens body 1 is connected with the zoom demand device 2 and the focus demand device 3 by using cables 4 and 5, each of which is normally prepared, includes approximately 20 wires, and has a length of approximately 1 meter.
In the conventional technology described above, the lens body 1 is connected with the zoom demand device 2 and the focus demand device 3 by using the multi-wire cables 4 and 5. When multiple demand devices are to be further connected with the lens body 1, cables equal in number to the demand devices are required.
For example, there may be crane photographing in which a camera and a lens are provided to the tip end of a crane whose length is approximately 3 to 5 meters and demand devices are operated for photographing by a camera operator at the base of the crane. There may also be photographing of savage animals at a distance from a camera and a lens which are installed in nature. In such cases, the length of the normal cable provided between the lens body and the demand device is insufficient, so it is necessary to manufacture and install a special extension cable. Therefore, the manufacturing and installation of the specific extension cable require cost and time. Cables each including as many as approximately 20 long wires are installed to correspond to the number of demand devices, which takes time and labor.
It is desired that an operational mode can be changed according to a photographing situation by instant switching between the tripod operation and the shoulder-mounted operation in a case where a single television camera and a single television lens are used. In the case of the tripod operation, the television camera and the television lens can be instantly removed as a unit. However, in the case where the zoom demand device and the focus demand device are used, until the connection cable is removed from the television lens, the shoulder-mounted operation cannot be performed, so the instant switching cannot be made.